The present invention relates to fluorosilicone compositions and more particularly the present invention relates to the use of fluorosilicone composition in defoaming crude hydrocarbon stocks.
Diorganopolysiloxane fluids are well known. Generally such fluids comprise a diorganosiloxane polymer with a viscosity varying from 10 to 1,000,000 centipoise where the polymer is triorganosiloxy end-stopped or silanol end-stopped. More preferably the polymer is triorganosiloxy end-stopped. The organo group in such a polymer may be selected from alkyl radicals, mononuclear aryl radicals, cycloalkyl radicals, alkenyl radicals and fluoroalkyl radicals such as 3,3,3-trifluoropropyl. Equally well known is the use of dimethyl polysiloxane polymers having viscosity in the range of anywhere from 10 to 500,000 centipoise as defoamers for various systems. Accordingly, such dimethylpolysiloxane polymers are well known defoamers for gas, oil separators; for glycol dehydrators; delayed cokers; Udex units where foam formulations are usually encountered in the stripper and extractor in units using diethylene and dipropylene glycol as extractor solvent thus reducing the capacity of the unit. Other units or processes in which defoamers are applied are vacuum tower units; propane deasphalting; and unit start-up in a refinery where units pumps may lose suction during the heating period due to foam caused by condensed water in the unit; amine scrubbing units; a furnace tube antifoulant and high detergent motor oils and asphalt processing and hot residuum storage in which the foaming limits the capacity of the tank and it may cause it to froth over outside the storage tanks.
These are just examples of various areas in which dimethylpolysiloxanes by themselves or with various other ingredients have been utilized to reduce the foaming in the apparatus or in the process. It should be noted that there are organic antifoamers. However, silicone antifoamers are preferred in that a very small amount has a substantial amount of defoaming activity. That is the silicone defoaming compounds are more efficient. Accordingly, dimethylpolysiloxane based antifoamers have been utilized in the above equipment and processes.
There are many types or variations of the dimethylpolysiloxane defoamers having a viscosity of anywhere from 10 to 500,000 centipoise. Thus, one type of composition is the emulsified dimethylpolysiloxane. Another type of defoaming composition has a filler such as a silica filler. Another type of defoamer composition that has advantages is one that has a small amount of a diorganopolysiloxane gum that is a gum having a viscosity of anywhere from 1,000,000 to 200,000,000 centipoise at 25.degree. C. However, such dimethyl polysiloxanes have their limitiations. Thus, the antifoamers are not very efficient in the defoaming of crude hydrocarbon stock such as crude oil. It was found that such compositions while the dimethylpolysiloxane fluid was soluble enough to accomplish the defoaming activity, nevertheless, didn't reduce the surface tension of the crude hydrocarbon stock sufficiently to cause it to result in efficient defoaming of the composition. There were some attempts in overcoming such deficiency by the production of new compositions. One attempt in overcoming such deficiency was to utilize a fluorosilicone homopolymer, that is a fluorosilicone homopolymer having 100 mole percent of methyl, 3,3,3-trifluoropropyl siloxy units. It was found when this compound was tried for defoaming purposes of crude hydrocarbon stocks that it was not sufficiently soluble and in fact even at elevated temperatures as high as 500.degree. F. was insoluble in the crude hydrocarbon and accordingly could not accomplish its defoaming purpose in the composition that was to be defoamed. Accordingly, since dimethylpolysiloxanes were inefficient defoamers for crude hydrocarbon stocks and since other silicone polymers such as the 100 mole percent of methyl 3,3,3-trifluoropropyl homopolymer was not soluble in crude hydrocarbon stocks so as to accomplish the defoaming of the composition, it was desirable to find a silicone polymer that would carry out the necessary defoaming of the crude hydrocarbon stocks. The necessity or desirability of doing this results from several considerations.
Crude hydrocarbon stocks are usually saturated with dissolved gases such as methane, hydrogen sulfide, sulfur dioxide, carbon monoxide, carbon dioxide and lower molecular weight olefines such as ethylene, propylene and butadiene. The gases are maintained in the solution by the pressure exerted by confinement. When the oil is pumped above ground the gases tend to be released. A number of these gases as pointed out above are valuable which may serve as the nucleus of a petrochemical business. Degassing to recover these gases is usually carried out in such a manner that gases can be effectively separated from the oil and collected. A separate crude oil distillation column can be used for these purposes. To assist in the desolution of the gases the oil is usually heated to 300.degree. to 500.degree. F. The elevated temperatures serve to lower the solubility of the gases in a crude oil medium plus reducing the viscosity of the crude oil. The rapid evolution of the dissolved gases may cause excessive foaming due to the high surface tension of the medium. The existing foam is detrimental and is separated and by means of entrainment, the foam is carried out into the receivers. Foaming is partially offset by the use of less vigorous column conditions. Unfortunately a concomitant loss in both column through put and separation efficiency are observed.
Accordingly, it was highly desirable to utilize an effective and efficient defoaming agent in such distillation column in the separation of a low molecular weight olefin from the crude hydrocarbon stocks, such that when they were separated there was a minimum of foaming or no foaming at all.
Accordingly, it is one object of the present invention to provide a method for defoaming crude hydrocarbon stocks.
It is another object of the present invention to provide an efficient defoaming agent for crude oil.
It is still another object of the present invention to provide an efficient method for defoaming crude oil with a fluorosilicone polymer.
It is an additional object of the present invention to provide a highly efficient defoaming agent for hydrocarbon stocks which defoaming agent is effective at high temperatures and is superior to prior defoaming agents. These and other objects of the present invention are accomplished by means of the invention as set forth herein below.